Urinary bladder radiotherapy-related chondroblastic osteosarcoma: Rare case report and review of literature.

Radiation-related osteosarcomas are well described malignant mesenchymal neoplasms, yet their pathogenesis is not fully understood. They are generally classified into either skeletal osteosarcomas, or their and rare soft tissue counterpart. The occurrence of osteosarcoma in the urinary bladder (UB) following radiotherapy is exceedingly rare. To the best of our knowledge, only two cases of radiation-related urinary bladder osteosarcoma have been published; we herein describe another case of an 85-year-old man who developed post radiotherapy chondroblastic osteosarcoma of the urinary bladder four years following initial surgical resection and radiotherapy for bladder urothelial carcinoma. We believe that this is the first case of radiation-related chondroblastic osteosarcoma arising in the urinary bladder. In addition, we review the literature and explore the possible histogenesis of this rare neoplasm.